Thursday, January 16, 2014

(Continued from Part 1, Part 2 and Part 3, from Nikkei Shinbun: Testimony of Dr. Madarame, in the third year of the accident: "Worst case scenario was possible for Fukushima" by Junichi Taki, editorial board member)

■「食い違いがあることに気づかず議論をしていた」

"We were talking past each other, and we didn't even know it."

――12日午後に１号機で爆発が起きたとき、どう思ったのか。

--What did you think when an explosion happened in Reactor 1 in the afternoon of March 12, 2011?

"I thought it was a hydrogen explosion the moment I saw the image. I don't remember clearly, but according to what Kenichi Shimomura, who was a cabinet counselor at that time, wrote, I calmly explained that "hydrogen leaked into the building, and since there is hydrogen (sic) [probably "oxygen"] in the building an explosion happened." I think it is probably true."

"From this explosion on, Prime Minister stopped believing me. He asked me if there were other experts at the Nuclear Safety Commission. I answered that Acting Chairman Yutaka Kukita was also knowledgeable. He told me to "call him here immediately". So I had Mr. Kukita come, and I returned to my office."

――１号機の爆発のあった時間帯は、海水注入の議論をしていたころでもある。

--Around the time of the Reactor 1 explosion, the debate was ongoing on seawater injection [into the reactors].

"In discussing the seawater injection, it would not be odd if I had been asked by Prime Minister whether there was a possibility of recriticality and I had answered there was a possibility. I have no memory of being asked."

"Even before the hydrogen explosion, Minister of Economy Banri Kaieda was chairing a meeting in the PM Reception Room (on the 5th floor of the PM Official Residence), and we were talking about the potential problems of seawater injection. I insisted that seawater be injected as cooling the reactor core was the first priority, even though it was not a long-term solution because of salt deposition and corrosion problem. I don't think Prime Minister would order a halt in seawater injection. The issue of halting the seawater injection arose, as pointed out in the National Diet accident investigation commission, from an arbitrary decision by TEPCO's Fellow Ichiro Takekuro. In any way, there was no halt thanks to Plant Manager Masao Yoshida."

"I realized later when I read books by politicians including Mr. Tetsuro Fukuyama (then-Deputy Chief Cabinet Secretary) that everyone had thought recriticality meant nuclear explosion. It is obvious from accidents like the JCO accident that even if criticality happens that's different from nuclear explosion. But we were talking past each other, and we didn't even know it."

――その日は深夜に自宅に戻るが、すぐにまた官邸に呼ばれる。

--You went home late that night, but was called back soon to the PM Official Residence.

"I hardly slept. But on March 13, I began to have more time [or "peace of mind"] to listen to other experts. Discussion with Dr. Kukita was particularly valuable, and we both agreed that the most frightening possibility at that time was the phenomenon called "High-pressure Melt Through" (HMT). HMT happens when the melted fuel melts the Pressure Vessel wall thin, and the melted fuel gets ejected through the Pressure Vessel due to the difference in pressure between the Pressure Vessel and the Containment Vessel. It is possible that the melted fuel could pierce through the wall of the Containment Vessel."

"After the hydrogen explosion of Reactor 3 on March 14, I advised that the relief safety valve of Reactor 2 should be opened quickly. I was worried that HMT might happen in Reactor 2, so I thought it would be prudent to equalize the pressure in the Pressure Vessel and the Containment Vessel. Plant Manager Yoshida insisted that preparation for the vent be done first. If the relief safety valve is opened, the water inside the Pressure Vessel becomes water vapor and flows into the Containment Vessel, leaving the fuel heated without water. So you cannot open the relief safety valve without preparation to inject water. It is a difficult decision."

――そう考えると、原子炉の底部から溶融燃料が落ちたのは不幸中の幸いと言えるか。

--In that sense, it was lucky that the melted fuel dropped from the bottom of the reactor.

Dr. Madarame on March 13, 2011:
3:40AM received call at his home from the secretariat of the Nuclear Safety Commission
5:00AM went to the PM Official Residence (after speaking with other commissioners at the Nuclear Safety Commission office)
The situation at the plant grew more serious as Reactor 3's high-pressure core injection system stopped.
10:04AM meeting of the Nuclear Disaster Response Headquarters
1:55PM went back to the Nuclear Safety Commission office, and explained the situation at the PM Official Residence
2:35PM went back to the PM Official ResidenceDiscussed the possibility of a hydrogen explosion in Reactor 3 with others including Mr. Yasui from NISA
3:30PM accompanied Chief Cabinet Secretary [Edano] in the press conference (would do a few more times later)
9:35PM meeting of the Nuclear Disaster Response HeadquartersDiscussed the worst case scenario [high-pressure melt through] with Deputy Chairman Kukita of Nuclear Safety Commission. Explained the core-concrete reaction after the melt through to the politicians

It is interesting to note that, according to Dr. Madarame's March 13, 2011 schedule, he was debating with another nuclear expert (Kukita) about the worst case of "high-pressure melt through", in which the melted core (corium) will eject from the Pressure Vessel at a high speed, possibly piercing through the Containment Vessel, while telling the politicians a more "benign" core-concrete reaction scenario.

Ventilation is not the cause of the Hydrogen explosions. The hydrogen problem and the melting fuel were the result of cooling failure. With, or without intentional venting attempts, the reactor and containment MUST ventilate in a LOC accident and it will. If it is not ventilated via the designed ventilation path, then the reactor and containment fail and the system ventilates at the weakest points. Intentional ventilation is a very dirty thing to do, but in this case, it was better than the alternative. Ventilation was not the evil thing that caused this mess.Operation of these NPPs is the problem. The problem continues.

About my coverage of Japan Earthquake of March 11

I am Japanese, and I not only read Japanese news sources for information on earthquake and the Fukushima Nuke Plant but also watch press conferences via the Internet when I can and summarize my findings, adding my observations.

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